This invention relates to materials and methods for detecting biomolecules in samples, and more particularly to a particulate solid phase having for encoding information concerning the assay, and to assays employing such a solid phase.
Solid phase assays have been used to determine the presence and/or the concentration of biomolecules, such as proteins, peptides, nucleic acids, carbohydrates and lipids. Solid-phase assays can be performed in a variety of fluids, e.g., simple buffers, biological fluids, such as blood, serum, plasma, saliva, urine, tissue homogenates, and many others.
In solid phase assays, small beads, or microparticles, are typically used as the solid phase to capture the analyte. Solid phase microparticles can be made of a variety of materials, such as glass, plastic or latex, depending on the particular application. Some solid phase particles are made of ferromagnetic materials to facilitate their separation from complex suspensions or mixtures.
In conventional solid-phase assays, the solid phase mainly aids in separating biomolecules that bind to the solid phase from molecules that do not bind to the solid phase. Separation can be facilitated by gravity, centrifugation, filtration, magnetism, immobilization of molecules onto the surface of the vessel, etc. The separation may be performed either in a single step in the assay or, more often, in multiple steps.
Often, it is desirable to perform two or more different assays on the same sample, in a single vessel and at about the same time. Such assays are known in the art as multiplex assays. Multiplex assays are performed to determine simultaneously the presence or concentration of more than one molecule in the sample being analyzed, or alternatively, to evaluate several characteristics of a single molecule, such as, the presence of several epitopes on a single protein molecule.
One problem with conventional multiplex assays is that they typically cannot detect more than about five analytes simultaneously, because of difficulties with simultaneous detection and differentiation of more than about five analytes. In other words, the number of different analytes that may be assayed simultaneously is limited by the solid phase.